The Internet has revolutionized the way networks are affecting corporate and home users. The growth in Internet is explosive and the number of users are estimated to be 40 to 50 million worldwide, and rapidly growing. Most of the home subscribers use analog modems, operating at 9600 bps to 33 kbps, to connect to the telephone company network. Analog modems are too slow, however, and make surfing the world wide web very time consuming, leading to frustration and diminished utility. Most of the users also turn off the graphics, because of the time required to transfer the images over the networks. There is, accordingly, an urgent need and demand by the subscribers to upgrade the line speed, but analog modems do not have much room to grow.
This has caused some vendors, including Amati, Aware, Analog Devices and Motorola, to develop and promote new types of digital modems which operate on the existing telephone lines (also called twisted copper pair or simply "twisted pair") and allow both the voice and data to travel on the same line simultaneously and at high speeds. These digital modems collectively have been named `xDSL` (Digital Subscriber Line). `xDSL` includes `ADSL`, `HDSL`, and `VDSL`. The most prominent and promising among them is `ADSL` (Asymmetric Digital Subscriber Line) operating at a relatively high speed of 6 mbps from the telephone company central office to the user, and operating at a lower speed of 640 kbps from the user to the telephone company central office, and thus, named asymmetrical. The reason for asymmetry in speed is that signal integrity can not be maintained if both directions run at the same high speed.
This is being promoted as the answer to all the frustration of the Internet users. The large scale deployment of this technology is expected to start in late 1997 and then grow exponentially in years to come.
Telephone companies prefer the `ADSL` as it allows them to use the existing telephone lines already connected to the homes and offices for voice, and yet simultaneously use them for data transfer, thereby saving cost.
`ADSL` standards have been approved and chip sets and modems are available, but such also has a major disadvantage; namely, that there is operation at high speed only one way, from the central office to the subscriber (download), which, however, is generally acceptable for a large number of subscribers, as most of the information is downloaded from the Internet to one's own computer. This, however, leaves out subscribers who also need to transfer significant data at high speed to the other subscribers (upload). The list of such users include:
Small Internet Service Providers(ISPs) who provide the information to the users, and need to transmit data at higher speed, not lower, as allowed with ADSL technology. PA1 Subscribers whose speed requirements (the preferred data transfer direction for the high speed channel) vary, such as someone who needs frequently to transfer large files (upload) to the central office for subsequent transmission to another subscriber on the network. The upload speed offered by the ADSL, as before mentioned, is 640 kbps from subscriber premises to the central office, which is roughly 10 times slower than the download speed PA1 Corporate networks where data usage pattern is similar in both the directions optimally requiring symmetrical speeds. PA1 a. by dynamically configuring direction assignment of high speed channel and low speed channel; and/or PA1 b by creation of a full duplex high speed channel and a full duplex low speed channel.
There has heretofore been no solution for these problems caused by the asymmetric nature of the ADSL. ISPs are required to lease from phone companies, very high speed dedicated channels to support their operations and at a very high cost. The subscribers with need to upload large files must continue to encounter a long delay, and the corporate networks simply use either dedicated leased lines or frame relay services, each of which is highly expensive.
The ADSL definition, therefore, appears to assume that most of the data flows from the central office to the subscribers, and thus matches the usage pattern of such a large number of subscribers.
What is not well served, however, as previously pointed out, are users with opposing data flow pattern needs requiring high speed from the users to the central office and low speed from the central office to the subscribers, or equal speed in both directions. A careful analysis of the ADSL reveals this technical limitation that both transmit and receive operations can not operate at high speed, though the actual assignment of low and high is not rigid.
The present invention is directed to overcoming these limitations with ADSL systems and doing so:
In the case of dynamically configurable speed assignment, the same physical line is used, but the uploading speed is swapped with the downloading speed by dynamically altering the digital signal processor parameters.
The preferred or best mode implementation requires the two existing telephone lines and then transforms them into two virtual lines (or also virtual twisted pair), each operating as a full duplex line. This, in effect, admirably connects the asymmetric speed ADSL into a virtual symmetric speed system by providing the capability of duplex swapping directions of the relatively high and low speed channels.